Ahmadinejad has boycotted cabinet meetings since Heider Moslehi, the intelligence minister, was reinstated after he was forced out of the government.

Moslehi was restored to the powerful post by Khamenei after Ahmadinejad had forced him to resign on April 17.

Ahmadinejad's opponents, meanwhile, have seized the opportunity.

According to the Shargh newspaper, a group of 216 lawmakers, more than two-third of the 290 members in the Iranian parliament, have issued a letter to Ahmadinejad, urging him to call off his cabinet boycott for the good of the country.

"You are expected to follow the supreme leader," the lawmakers wrote.

On Friday, a hardline cleric used his nationally broadcast sermon to indirectly warn Ahmadinejad that he would be moving into dangerous territory by escalating his challenges to Khamenei.

"Obedience to the supreme leader is a religious obligation as well as a legal obligation, without any doubt," Ayatollah Ahmad Khatami said. He did not mention Ahmadinejad by name, but it was clear he was referring to the president.

Unhappy clergy

Trista Parsi of the National Iranian American Council said: "There has been lot of pressure on Khamenei from some of the clergy who are very displeased with the very aggressive way that Ahmadinejad has expanded his own influence and influence of the executive branch at the expense of the clergy."

Heidar Moslehi is the point of contention between Khamenei and Ahmadinejad [Reuters]

"This was bound to happen sooner or later but the timing and the fashion in which it has happened is a little but more surprising."

The bickering has invited speculation that Khamenei's once-blanket support for Ahmadinejad - particularly in the critical months of chaos after the president's disputed re-election in 2009 - could be now fraying by his repeated attempts to push the limits of his powers.

Ahmadinejad's chief media adviser, Ali Akbar Javanfekr, wrote on his website on Friday that the president was very "concerned" that if he bowed to pressure, his "achievements" would be lost.

But he also stated Ahmadinejad would "eventually" return to work and put the issue behind him.

"We have seen Ahmadinejad backing down in the past but this time it would be far more embarrassing than on previous occasion. It's most likely he will once again have to back down but it will be far more costly for him than it was before," Parsi said.

"It's fascinating that it's taking place at a time when the Iranians are quite sensitive that any of the open conflict actually might facilitate the spread of some of the Arab protests in Middle East to come to Iran as well."